Semiconductor lasers are the fundamental building block in compact optic and optoelectronic devices. Formed from Group III-V semiconductors, the semiconductor lasers emit laser light in response to electrical stimulation as electrons relax back to lower energy states and emit photons. High brightness semiconductor lasers are generally single mode waveguide structures that are limited to a few hundred milliwatts.
Higher power devices are desirable. However, prior efforts to increase the power of conventional devices have met limited success. Tapered waveguide structures have been successful in extending power output to a few watts. Since the conventional semiconductor lasers are generally free expansion devices with no control over the position of the beam waist, the change in current used to effect the higher power has typically caused the beam waist to move around. This is undesirable since it causes the beam position to wander in the far field as well as the beam size.
Other devices such as the master oscillator power amplifier (MOPA) use a distributed Bragg grating to define a master oscillator, and the tapered section of the waveguide serves is a power amplifier. Such a device is difficult to fabricate and is not easily integrated into linear arrays of devices. These conventional attempts also tend to demonstrate a strong astigmatism that is often uncontrolled.
Accordingly, there is a need for an improved semiconductor laser structure. It is an object of the invention to provide such a structure to address some or all of the aforementioned drawbacks.